The prior art has disclosed various approaches for securing bolts in concrete. For example, U.S. Pat.No. 913,876 is directed to internally threaded sections gas pipes which are embedded in concrete so that a bolt may then be screwed into it.
U.S. Pat. No. 333,388 also uses a tubular body with internal threads. The body is embedded in cement to receive a threaded bolt which is used as an anchor for a wall plate or cap.
U.S. Pat. No. 3,993,341 utilizes a vertical bushing mounted on a horizontal plate for receiving a bolt for lifting a slab.
U.S. Pat. No. 4,117,643 is directed to a sleeve which is embedded in concrete. The sleeve has internal threads for receiving an anchor bolt.